myelin

a sheath of phospholipid (see LIPOSOME ) and PROTEIN that surrounds the axons of some NEURONS . It is formed by specialized CELLS known as Schwann cells, each of which encloses the axon in concentric folds of its cell MEMBRANE . These folds then condense to form myelin, the neuron then being described as myelinated. Schwann cells produce myelin at regular intervals along the length of the axon, and electrical impulses pass more rapidly along myelinated nerve fibres than along non-myelinated ones.